Electric lamp



f A 1551524 E.. FRlEDERlCH ELsc'rnxq LAMP Aug. Z5, 1925.

nud hug. 50, 1921 .'b'y an inertgas or vapor,'and so Patented Aug. 25,,1925.

UNITED STATES PATENToFFlcE.

-ERNST FRIEDERIGH, 0F BERLIN, GERMANY, ASSIGNOR, BYIIESNE ASSIGNMENTS,T0. GENERAL ELECTRIC COMYANY, 0F SICHENECTADY, NEW YOP-K, A CORPORATION0F New YORK.

sanering LAMP.

Appucauan med August so, mai. "smal no. 496,942.

(ensures ummarnarnovrsxous or rma ser or man s, m1, 41 sur. L., ma.)

To all whom it may concern: Y

Be it known that I, ERNST FRIEDERICH, a

citizen of Germany, residing at Berlin, Ger

many, have invented certain new and useful Improvements in ElectricLamps (for which applications for patents have been ledin Germany, June3, 1914, A26055, VIH/21 f, and August 13, .1914, A215383, VIII/2U;Hungary, May 22, 1915, and August 13, 1915;` Switzerland, May 22, 1915,and August 10, 1915; Netherlands, May-28, 1921, and August 10, v1915;Sweden, June 2, 1915,' and August 11, 1915;, Great Britain, June 3,1915,and August 1,2, .1915; Japan, March 4, 1920,and March 11, '1920;Austria, May 31, 1915, vand'August 23, 1915), of ,which the following isa specification.

The' present invention relatesfto electric lighting, and moreparticularly'to a lamp in which an are is operated in an enclosedenvelope between electrodes of highly fractory metal, such astungsten-surrounded PI'OPQI" tioned -that they will be heated descence.v- One ofthe objects ofmy invention is to provide means for'starting thearc in a lamp of this nature. A further object of my invention is tolprovidean improved arrangement of electrodes whereby a higher operatingefficiency, a. longer life and a better lightdistribution may beobtained.

The novel features; omy invention with further objects and vantages will.best be understood by .reference to the-following description taken inconnection with the ae- -lrcompanying drawing in which. Fig. 1illustrates a lamp equipped with one of my imm proved starting devices;Fig. 2 shows -a modification thereof inwhich two vsets of electrodes areAconnected in series and in which electrodes of an improved formi areemployed;-v Fig. 3 is a view of the supportf ing arrangement for theelectrodes o the lamp shown in Fig. 2 taken at a right angle tothe viewindicated in Fig. 2; Fig. 4 is a bottom v iew of'the arrangement used`in Fig. 2`for starting the lamp; and Fig. 5is an enlarged detail viewof one pair of the `electrodes of the lamp shown in Fig..`2 with 'thestarting conductor which bridges them when the lamp is not'in operation.Fig; 6 is a` wiring diagram of the arrangementshown 1n Fig. 2.

the arc in lamps of th1s nature because of the fact that a highervoltage is required to bridge the gap between the electrodes to startthe are than is required forits normal removlng an intermediateoonductin mem. 'ber which. bridges the electrodes w en the lamp is notin operation, provided` a suit-- 'able' material is used for thisbridging mem- Diiculty has been experienced in starting 55 operation.Neither can the arc'bereadily 60 l ber. .Among the materials -which ma-be used for this purpose are metals which v materials which are moresuitable are oxides which are good Aconductors when cold, such iiiuranium-oxide, vanadium oxide and the 1 e.

The method of operationof vmy-improved VQ 70 a higher electronicemission than tungsten starting device may' perhaps be explained 80- asfollows:

0f the conductive bridging member some portion, though very small, willcling to the refractlf electrodes by the mechanical pressure of thecontact or by fritting as soon as the`part which is in contact becomesheated byits resistance when the circuit is closed. At these particlesthe arc starts and easily-persists in consequence of the suitability ofthe material. These small particles 9 of course are vaporized rapidlybut in the meantime the temperature` of the electrodes has risen sorrapidly that they themselves now maintain the arc continuously andreliably. With respect to the conducting oxides it is possible that thesuitability of such materials may for myY purpose be explained b thewell-known phenomenon thati drop across the electrodes. The conductiveuranium oxide having a formula ljOz'fis particularly well adaptedvforthezprgsent pur- 'such 'exi esas soon asthey become heated emit large-numbers of electrons and on this 10 'account reduce to a'large extentthe'v voltage in comparison with that of the anode has' still anotheradvantage. In lighting lamps ol' this nature it is necessary that thecathode shall tlrst be heated to a high temperature. It the 'cathode is-of small area inI compari' on with the anode-and the lamp is to be'started by bringing the electrodesv in contact and withdrawing them,'thecathode will become more highly heated at the contact point by reasonof"its small size and higher resistance, and on this account it1vbecomes possible to start the arc by merely bringing the electrodestogether and separating them. This advantage is also present when thelamp is lighted by the use of an auxiliary electrode or if it is to belighted by removing a bridging rmember as heretofore described.

Itwill o `eurse be understood that the methode starting which I havedescribed is in no way limited to spherical electrodes as other forms ofelectrodes, helical for exalnl'ple, may equally well be employed. It wialso be apparent that many variations -may be made in the particulararrangement used for withdrawing the bridging member from contact withthe electrodes.v

' 35 of a. sealed envelope having thereinI electrodes of-highlyrefractoryv metal separated -by ashortgap and so proportioned as to be.heated to mcandescence by the passage of an arc between them, thesurface area of the 40 electrode which serves as a cathode being" sosmall with respect to that of the anode that Iwhen the lainp is inoperation the temperatur ofthe cathode is maintained higher than that ofthe anode.

-2. An electric lamp comprising a sealed envel e having thereinspherical electrodes of hig ly refractory meta'l separated by a` shortgap and so proportioned as to be heated to incandescence by the passageof L an arc between them, the electrode which 'serves as a cathode beinglarger than the one which serves as anode whereby when the lamp is inoperation the temperature of the cathode is maintained' higher than thatof the anode.

3. An electric lamp comprising a sealed envelope having thereinspherical electrodes of highly refractory metal' separated by a shortgap and so proportioned as to he 80 heated to incandescence by thepassage ot an arc between them, vthe electrode which serves as a cathodebeing larger than the one-which serves as anode,. whereby when the lampis in operation the temperature-of the cathode is maintained higher thanthat of the`anode, and means forstarting an arc between said electrodescomprising a body electrodes when the lamp is, not in operation andwhich is automatically withdrawn from -said bridging position whencurrent starts toflow in said lamp.

il. In an arc lamp a sealed envelope, a`

pair of electrodes of solid refractory metal adapted to be connected toa source ot current, said electrodes separated by a gap, a solid arcstarting element bridging the gap and being in contact with the tw'oelectrodes before the arc is established and electromagnetic Ameans forseparating the element from the electrodes for establishing the arcbetween the electrodes andlor holding the element from across the gap aslong as the arc isv established, the surface of said element having ahigher electronic emission than the metal at the same temperaturewhereby the arc -may be established at a `ot conducting material whichbridges said y lower voltage than when the electrodes are brought intocontact directly.

5.In an arc lamp asealed'envelope, a pair of electrodes of refractorysolid metal adapted to be connected to a source of current, saidelectrodes separated by a gap, an arc starting element forming Contactwith the electrodes and bridging the gap, electromagnetic means forstarting 'the arc between the electrodes by withdrawing the element fromacross the electrodes and formaintaining the element out of engagementwith the electrodes while the arc is in operation. said element beinginthe form of .a solid the surface of which is adapted to yield anelectronic emission sufficient to start the arc between the electrode ata lower voltage than if the electrodes are brought into contact directlyand separated, said envelope containing a gas which is inert withrespect to the electrode.

6.' In an arc lamp a sealedenvelope, a. no

pair of electrodes of tungsten adapted to be connected to a source ofcurrent. said electrodes separatedvby a gap, asolidvarc starting elementbridging the gap and being in contact ywith the two electrodes beforethe arc is established and elcctromagnetic'means for separating theelement from the electrodes for establishing the are between theelectrodes and for holding the clement from across the gap as long asthe arc is established.v the surface of said element having a higherelectronic emission than the metal at the same .temperature whereby the,arc' may be established at n .lower voltage than when the electrodes arebrought into conl tact directly.

7. In. an arc lamp a sealedenvelope, a pair otfelectrodes of tungstenadapted to beconnected to a source of current, said electrodes separatedby a gap, an arc starting element forming contact with the elec- ERNSTvogage chan mt@ com/act

